When you're in a relationship, you're in a state of entanglement with your partner. But, just like in quantum superposition, you can exist in many states at once: being happy, being sad, being bored, and being confused all at the same time.
But then, one day, you're like, "Wait, no, I'm only in one state. And it's not happy." And that's when you start to decohere. It's like, you know, when you're all like "I thought we were in superposition, but now I'm just in one place... alone."
Don't worry, it's not the end of the world. You can always measure the damage and try to interfere with the situation.
Or, you know, you can just collapse and let it all fall apart. It's like, quantum superposition, but with more tears.